Thermal stability of a Barium Titanate - Calcium Titanate mixture, calculated from mixing enthalpies (DFT) and configurational entropy; depicted for a neutral structure, in comparison to a positively charged and negatively charged structure (realized by including one additional hole or electron per 2x2x2 supercell). Qualitative first results suggest that electronically compensated dopants may be used to increase or decrease miscibility at a given temperature.